Pentiptycene-based polyimides with Hierarchically controlled molecular cavity architecture for efficient membrane Gas separation, Journal of Membrane Science, http://dx. ABSTRACT:A series of new pentiptycene-containing diamines with systematically varied substituent groups were designed and synthesized with high purity and high yields. These diamines were used to prepare a series of new polyimides with 4,4'-hexafluoroisopropylidene bisphthalic dianhydride (6FDA) by conventional condensation polymerization. The obtained pentiptycene-containing polyimides possessed high molecule weights, excellent thermal stability, good solubility in a wide range of organic solvents and thus excellent processability for membrane fabrication. Because of the excess amount of internal free volume associated with the molecular cavities in the pentiptycene moieties and the consequently disrupted chain packing, all the polyimides exhibited high fractional free volume (FFV) leading to high gas permeabilities as well as good selectivities that are highly desired for gas separation membranes. In addition, the comparisons between the pentiptycene-containing polyimides bearing various substituent groups indicated that free volume, the vital structural parameter for fast and selective molecular transport, was very sensitive to the size of the substituent groups. Large substituent groups such as CF 3 led to increased FFV, while relatively small substituent groups such as CH 3 resulted in reduced FFV, possibly due to the mechanism of "partial filling" of the molecular cavities of pentiptycene units by the substituent groups. Gas permeability data also supported this unusual trend of the dependence of free volume on the substituent groups. This finding provides a completely new and potentially novel means of molecular-level manipulations to predictably construct preferred free volume architecture that may 2 maximize the separation performance of polymeric membranes. Keywords： ： ： ：pentiptycene, polyimides, free volume, gas separation membrane Highlights • Robust and highly soluble pentiptycene-based polyimides were synthesized • Pentiptycene-based polyimide membranes showed high fractional free volume • Architecture of the molecular cavities was finely tuned by substituent groups• "Partial filling" mechanism was proposed based on free volume studies• Pentiptycene-based polyimides show high permeability and high selectivity

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Narrow‐bandgap n‐type polymers with high electron mobility are urgently demanded for the development of all‐polymer solar cells (all‐PSCs). Here, two regioregular narrow‐bandgap polymer acceptors, L15 and MBTI, with two electron‐deficient segments are synthesized by copolymerizing two dibrominated fused‐ring electron acceptors (FREA) with distannylated aromatic imide, respectively. Taking full advantage of the FREA and the imide, both polymer acceptors show narrow bandgap and high electron mobility. Benefiting from the more extended absorption, better backbone ordering, and higher electron mobility than those of its regiorandom analog, the L15‐based all‐PSC yields a high power conversion efficiency (PCE) of 15.2% when blended with the polymer donor PM6. More importantly, MBTI incorporating a benzothiophene‐core FREA segment shows relatively higher frontier molecular orbital levels than L15, forming a cascade‐like energy level alignment with L15 and PM6. Based on this, ternary all‐PSCs are designed where MBTI is introduced as a guest into the PM6:L15 host system. Thanks to further optimal blend morphology and more balanced charge transport, the PCE is improved up to 16.2%, which is among the highest values for all‐PSCs. The results demonstrate that combining an FREA and an aromatic imide to construct regioregular narrow‐bandgap polymer acceptors provides an effective approach to fabricate highly efficient all‐PSCs.

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A simple approach to fabricate high-efficiency annealing-free poly(3-hexylthiophene): [6,6]-phenyl C(61)-butyric acid methyl ester (P3HT:PCBM) solar cells is reported by using p-type CuI to substitute PEDOT:PSS as anode buffer layer. It is found that the P3HT:PCBM blend films deposited on CuI surface show different orientation of crystalline P3HT domains and phase separation from those deposited on PEDOT:PSS surface. A nanoscale phase separation of P3HT and PCBM with domain sizes about 10-30 nm is formed for the P3HT:PCBM blend films deposited on CuI surface. Absorption and grazing incidence X-ray diffraction (GIXRD) experiments indicate that the CuI layer not only induces the self-organization of P3HT chains into well-ordered structure but also results in the vertical orientation of π-π stacking planes of P3HT with respect to the substrate which is favorable for the hole collection in polymer solar cells. Hole-transport investigation discloses that hole mobility of the as-spincast P3HT:PCBM blend film on CuI surface is increased with 3 orders of magnitude compared to the P3HT:PCBM film deposited on PEDOT:PSS. A power conversion efficiency of 3.1% for the as-spincast P3HT:PCBM solar cell with CuI buffer layer is about 4-fold enhancement compared to 0.83% of the control device with PEDOT:PSS, and is comparable to the reported P3HT:PCBM solar cells subjected to post thermal treatments. This work implies that interfacial engineering is a promising approach for manipulating morphology of active layer and can potentially simplify the process and shorten the fabrication time of polymer solar cells in low-cost roll-to-roll manufacturing.

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